1. Field of the Invention
The present invention relates to a separator of solid polymer electrolyte fuel cell, and it relates to a resin molding method for a portion of the separator.
2. Description of Related Art
In recent years, fuel cells are known as driving sources for automobiles or the like. In typical fuel cells, separators are applied to both sides of a plate-shaped electrode (MEA: Membrane Electrode Assembly) so as to form a, layered structure (cell) as a unit, and plural units are stacked to form a fuel cell stack. The MEA is a three-layered structure that a polymerized electrolytic membrane, which is made of an ion-exchange resin or the like, is held by a pair of gas diffusion electrode plates (positive electrode plate (cathode) and negative electrode plate (anode)). The gas diffusion electrode plate is structured such that a gas diffusion layer is formed on the outside of a catalytic layer which contacts the polymerized electrolytic membrane. The separator is layered so as to contact the gas diffusion electrode plate of the MEA. Gas passages for circulating a gas and coolant passages are formed between the gas diffusion electrode plate and the separator. In the fuel cell, for example, hydrogen gas as a fuel is supplied to the gas passages facing the gas diffusion electrode plate at the negative electrode plate side, and an oxidizing gas (oxygen, air, or the like) is supplied to the gas passages facing the gas diffusion electrode plate at the positive electrode plate side, and electricity is thereby generated by electrochemical reaction.
The separator should have characteristics that electrons generated by the catalytic reaction of the hydrogen gas at the negative electrode plate side are supplied to an external circuit, while electrons from the external circuit are supplied to the positive electrode plate side. Electrically conductive materials such as carbon-containing materials or metal-containing materials are used as the separator. In particular, the separator made of the metal-containing materials is superior in mechanical strength, and the weight reduction and the size reduction thereof can be performed by the thickness reduction. Thus, the separator made of the metal-containing materials is advantageous. The separator made of the metal-containing materials is produced such that thin plates of stainless steel used as a material are formed so as to have a corrugated cross section by press forming, and grooves formed on the surface and the rear surface thereof are used as the gas passages and the coolant passages.
In separators, a resin member is partially provided at a peripheral edge portion of separator as a positioning member used in layering, a guarding and reinforcing member for movement prevention of the cell due to collision, or the like. In this case, the resin member may be connected to the peripheral edge portion of separator by using an adhesive. However, in this method using the adhesive, since the resin member is separately produced, and it is applied to the separator by using the adhesive, the production cost is higher. In addition, hardening of the adhesive is time-consuming, and it is difficult to obtain a high connection strength. Since the adhesive is used for the connection of the resin member and the separator, there are limits for improving size accuracy.
In order to solve the above problems, a method has been proposed in which a resin is molded at a peripheral edge portion of separator so that molding and connection are performed simultaneously. For example, as a technique in which a resin is molded to a thin parts of metal or the like, a resin molding method has been known in which a parts is set in a die, and a resin is injected to the die (for example, Japanese Unexamined Patent Application Publication No. 2004-58442).
In the resin molding method in Japanese Unexamined Patent Application Publication No. 2004-58442, the overall of the parts (which is an electronic substrate in Japanese Unexamined Patent Application Publication No. 2004-58442) is provided in the die, the resin is injected in the die, so that almost overall of the parts is molded by the resin. When this method is used such that the resin is molded at only the peripheral edge portion of separator, the peripheral edge portion of separator is held between two dies, and the resin is injected. In this method disclosed in Japanese Unexamined Patent Application Publication No. 2004-58442, the resin molding is not performed on the overall of the parts which is the separator. Due to this, when force is applied from the peripheral edge portion of separator to the outside, a resin member formed by this method may be separated from the separator, and it may be fallen down. That is, it is difficult to secure the connection strength of the separator and the resin member.